Harrow disk



, Mmh4, 1947. w.H.FARR 2,416,742

HARROW DISK Filed .Ia'n. 9, 1943 FIG. Z.

8 INVENTOR Warren H. Farr.

A TTORNEY 'Patented Mer. -4, 194'/ HAnRow msx warren n. Farr, Detroit, Mich., assigner to The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania'.

Application January 9, 1943, Serial No. 47,1,851

2 Claims. 1

This invention relates to harrow disks and particularly to a method and apparatus forheat treating steel disks for harrows and similar uses.

Metal requirements for harrow disks are exacting because of the rough usageto which a harrow is ordinarily subjected. Thel disk in the y usual type harrow must be of metal strong enough to resist curling under the harrow weight; it must resistl kinking and nicking due to impact on pebbles or other hard materials; and it should l vto heat treatment in accordance with this in y vention, the measurable degree of yield or'springported for heat, treatment. Steel disks of the desired type have preferably such a carbon con, y

tent, as .to possess, in their normal state prior iness under load,l associated with toughness,

' which 'will afford adequate resistance to impact retain its shape and yet possess a certain amount of springiness. Finally, the edge should beable to withstand hard treatment and maintainv its cutting qualities. I

Carbon and alloy steels are preferable Vas harrow disk metals, and the heat treatment should b'e such as to develop the above-mentioned qualities.. Frequently, the steel is rolled two ways to develop resistance yto bending. Electrical heat treatment lends itself satisfactorily to the securing of appropriate hardness.

Associated i' with the securing of the desired4 improved process for electrically heat treating harrow disks. A further object is to provide a simplified process for securing diierential heat treatment on opposite sides of the edge portion of a disk. An object, also, is to provide a process in which the desired edge curvature of the.

harrow disk is obtained automatically. Additionally, an object of the invention is the provision of simplified quenching means for heated articles.

Further objects relating to the invention will appear on consideration of the following detailed description of the process, apparatus and article, and of the illustrative embodiment ofthe apparatus and article, such as appears in the accompanying drawing in which:

Figure 1 is a vertical section through the disk and supporting mechanism:

Figure 21s a plan view of the structure; Figure 3 is a detail showing the conductor and coolant connections; and

Figure 4 is a detail of the support. Referring to Figures l and 2o! the drawing, there is shown an assembly by means of which the metal at diierent angles so as to distribute f the internal stresses with greater uniformity, this being particularly desirable in a disk or wheel subjected to pressure along the entire peripheral edge. 4

The disks I0 areadapted for heat treatmentl on an inductive heater, generally indicated by' the numeral I2, and comprising a single primary coil I4 having spaced integrally and radially projecting lugs I6, extending from the outer surface of the primary coil, and supported on standards I8. The mode of connection between the lugs I6 and standards I8 is clearly' shown in Figure. 4, a machine screw 20 passing through an eye opening in the lug and having screw-threaded engagement with the top of the standard I8. An insulation sleeve 22 and insulation Washers 24 electrically insulate the lug from the standards,f these elements being held in position by the bolt Washers 26.

As indicated .in Figure 1, the primary coil is 30 in close proximity, the tubular cross-section y being closed by means of end plates 32. .Conductor terminals 34 and 36 lead fromy the circular ends 30 of the primary coil, power line connections'supplying high-frequency current in excess of 2000vcyclesand preferably around 9600 cycles being made to these terminals by means of screw bolts 38, two bolts being utilized for each terminal. As shown in Figure 3, the te'rminals 34 and 3 6 are formed with passageways 38 and 40, connecting with the hollow interior of the primary coil I4, and' to these passageways pipe connections 42 and 44 are made for the passage of an appropriate coolant through the primary coil.

The disk I0 is vmounted upon rotatable supporting means centrally positioned within the annular primarycoil. These supporting means,

the disk I0, as indicated dotted outline, is supindicated generally by the numeral 50, include I0, the end of the shaft 7 proper control over the quenching liquid,

now appear. Electrical power is then applied to a stationary tubular and i ber 52, the top of which terminates within the levels of the top and bottom planes of the primary coil. Within the tube 52 is positioned a shaft 54 having a reduced upper section 56,

which is connected to the tube 52 by means of ball bearings 58 and ball bearing runways 5Il.` A threaded plate 62 normally holds the ball bearing upstanding frame. meml unit in position. Also connected tothe reduced .'upper section 56 of the shaft is a vdisk-supporting member 64, having a tubular skirt 65 de'pend- `ing therefrom and rotatable therewith. VResting A onthe flattened top of this vmember 64 isv the disk 54 being formed with a rectangular section 68, adapted to enter a corresponding central square opening in the disk I0. A holding nut 'IIL'- provided with a pin 12 for engagement of a bayonet slot 14, in the top c I annulus.. The apparatus as above described may.

be secured, as by boltsII, to a circumferential base plate I3, having radial openings I spaced from the supporting elements I8. v v Having described the essential apparatus for ,carrying out the process steps of my invention,

direct a broad fan-shaped sheet Y 4 u v` K results in the concentration'of heat on the lower side of the disk, asV shown in Figure 1, thedisk expands more rapidly on vthe lower edge annulus,

warping the same upwardly and, because of the uniform electrical action around the'disk circumference, the warping curvature lis lsubstantially uniform. The heattreatment is continued for such a-time periody that the temperature of the edge annulus 90. as distinguished from the central annulus 92, is above thecritical temperature of the material, that is, labove the temperature at which molecular rearrangement, duev to heat, occrs. It is important that the' heat be carried above this critical temperature in order 'to secure the proper hardness on quenching and fiiiu'ltgher to prevent asubsequent flattening of the Having heated the disk t0 the proper temperatu're for the desired time-interval, tneelectrical power'is cut volf and the quench immediately applied. There consequently -results' a contraction of the disk, the contraction concentrating in the` edge annulus with-a resultthat a pronounced dishing of the disk occurs, as shown' by the *disk 94` in Figure 1. vDue to the rotation, of thedisk,

lthe quench liquid is carriedtolallfparts 'of ,the

heated section of the .edgenannulusjandthe quench -is continued until theidiskv is reduced tov ambient temperatures. lIn accordance with is lquenched from a higher l'temperature than the vupper surface 98, and whileboth surfaces .of the the operation of the same may now be described 'in detail.

A net disk lo, having been appropriately rolled and treated to provide the necessary compression and impact resistance for the central V'annulus v or area of the diskother than theedgev annulus hereinabove mentioned, is clamped to the rotatable shaft 54. The shaft is then rotated by'any appropriate means with speeds sufliciently high to secure uniformity of heat treatment in the time interval, as required',v and to secure the as will the primary through the terminals 34 and 36; the coolant in the primary coil being under forced movement, with the result vthat high-frequencyv is applied to the edge 4' electromagnetic -induction annulus of the disk I0.'

a As is known in this art, the application of a high-frequency alternating current in inductive relation to a conductor, such'as disk '|(I, induces in the conductor eddy currents variable withfrequency, the same constitutingv a` heating means `of high effectiveness; due to the skin effect phenomena, heating currents tend to concentrate in the surfaces of the disk, and where the conductorand inductor are closely' positioned together, as in the present arrangement, the surface of the disk adjoining the inductor receivesV Aamaximum concentration of heat, due to the so-called proximity effect, that is, that effect due -to v the summation of the inductive effects,fby which the reactive magnetic forces at the a4djacent surface of the disk I0 are lessened, permitting .a larger flow of current and consequent increase. in heating action at the adjacent or under surface.

Due to the heating eiect'which, as described,

` junction with the edge annulus possess compressional stresses, the

stresseson the lower edge `96 -exceed ythoseon the Further, the' x compressional a upper edge` ',98.

thendesc'ribedheat treat'-y ment, the lower surface 96 of theedge annulus stresses in the edge annulus' 9 0'. are materially in excess of the stresses existing in the central annulus 92.- Therefore, on cooling, any 'tendencv to atten on thel part of a disk is resisted, and thedisk retains, therefore, av pronounced curvature. -Ifthis curvature is not of the desired egtent, the heating and quenching may be repeated. 'Unless the critical temperature of the material isv exceededV in the heat treatment, this result usually'wouldnot be obtained. As a result of this heat treatment, the completed disk possesses anl edge annulus of uniform hardness in conmore yieldable and tougher central annulus 92, thus making the disk highly adaptable for use in harrows and similar uses.

It is pointed out that through the use of the y spout V82 on thequenching pipes 80, the quench quench liquid'is placed directly adjacent the area, be-

tween the vdisk-edge andthe inductor I4, so

that considerable pressure canbe applied to pre-v vent the formation of steam pockets in this area.l

Avoidanceof'stearn pockets where water is used is `also facilitated by the rotation of the disk as -well as by the upward bending of the disk edge to form a flared space for the quenching liquid.

The drawing and description thereof are intended to illustrate-an embodiment of the invention which may be preferred. vHowever,

modifications of the same may be made such as may come Within the scope of the claims hereto l appended'. What is claimed is:

1. Adished-steel disk having an edge annulus hardened after heating above the critical temperature for steel, the convex annular sur. face having a hardness greater than that of the concave annular surface.

2. A dished -steel disk havingv an 'edge'annulus quench hardenedv after heating above the critical temperature for steel, the convex annular survface having a hardness greater than the concave REFERENCES CITED The following references are of record in the file offthis patent:

UNITED STATES PA'I'ENTS Number Name Date 488,514 Arnold Dec. 20, 1892 1,325,770 W00d1n Dec. 23, 1919 vNumber Number Name Date Corbin Oct. 17, 1893 Mott et al. Sept. 2, 1941 Junkers Dec. 2, 1924 Doelker June 10, 1948 Verity May 22, 1934 Davis May 7, 1929 Denneen Apr. 21, 1942 FOREIGN PATENTS Country- Date British 1936 British July'23, 1937 Austrian May 30, 1932 

